Messages in this thread | | | Date | Mon, 27 Feb 2023 15:46:50 +0100 | From | neil.armstrong@linaro ... | Subject | Re: [PATCH v1 0/3] Meson A1 32-bit support |
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On 27/02/2023 15:28, Dmitry Rokosov wrote: > Hello Neil! > > On Mon, Feb 27, 2023 at 09:15:04AM +0100, neil.armstrong@linaro.org wrote: > > [...] > >> I'm aware Amlogic also runs their kernel as 32bit to gain a few kbytes >> of memory, but those processors are ARMv8 and the arm64 arch code >> has been designed for those CPUs. >> >> So far I didn't find a single good reason to add 32bit support for >> ARMv8 Amlogic based SoCs, if you have a solid reason please share. > > I totally agree with you, but I suppose it's fully related to 'big' > Amlogic SoC like S905_ or A311_ series. A113L (aka 'a1') is > a cost-efficient dual-core SoC which is used for small, cheap solutions > with cheap components. Every cent is important during BoM development. > That's why usually ODMs install small ROM and RAM capacity, and each > megabyte is important for RAM/ROM kernel and rootfs footprints.
Do you have figures ? is 32bit ARM kernel really lighter when ARM64 one is correctly configured ?
> Why am I talking about rootfs? For such small projects a good > choice is buildroot rootfs assembling framework. Unfortunatelly, > buildroot doesn't support 'compat' mode when kernel and userspace have > a different bitness.
well this is a buildroot problem... the kernel itself is perfectly capable of running an AArch32 userspace.
> In the internal project, we save several > percents of ROM/RAM free space using 32-bit configuration (mostly rootfs > ROM space, to be honest). Therefore, for such 'little' cost-efficient > SoCs we can make an exception and support 32-bit configuration, from my > point of view.
32bit ARM is now "legacy", I would need to have an advice from the ARM SoC maintainers, but AFAIK new ARMv8 SoCs should stay in arm64 arch.
Arnd ? Olof ? do you have an opinion on this ?
> > What do you think about that?
>> >> And as Krzysztof stated, the support is incomplete and cannot work >> without a dts file. > > Agreed, we shouldn't merge dead code. But there are several question to > discuss there. Please check my reply to Krzysztof message. > > [...] >
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